ii. Pneumonia :is th inflammation of lungs caused by bacteria Diplococcus pneumoniae, in which the air sacs fill with pus and may become solid

iii. Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. In this disease, walls present in between the alveoli break, as a result gas exchange area of the lungs is reduced. It may be caused due to oedema, inflammation or mucus deposition in the bronchi.

iv. Cough : It is the expelling of air from the lungs with a sudden sharp sound.